Polysomnography, also called a sleep study, is a test used to diagnose sleep disorders. Polysomnography records your brain waves, the oxygen level in your blood, heart rate and breathing, as well as eye and leg movements during the study.
Polysomnography usually is done at a sleep disorders unit within a hospital or at a sleep center. You’ll be asked to come to the sleep center in the evening for polysomnography so that the test can record your nighttime sleep patterns. Polysomnography is occasionally done during the day to accommodate shift workers who habitually sleep during the day.
In addition to helping diagnose sleep disorders, polysomnography may be used to help adjust your treatment plan if you’ve already been diagnosed with a sleep disorder.
Why it’s done
Polysomnography monitors your sleep stages and cycles to identify if or when your sleep patterns are disrupted and why.
The normal process of falling asleep begins with a sleep stage called non-rapid eye movement (NREM) sleep. During this stage, your brain waves, as recorded by electroencephalography (EEG), slow down considerably.
Your eyes don’t move back and forth rapidly during NREM, in contrast to later stages of sleep. After an hour or two of NREM sleep, your brain activity picks up again, and rapid eye movement (REM) sleep begins. Most dreaming occurs during REM sleep.
You normally go through four to six sleep cycles a night, cycling between NREM and REM sleep in about 90 minutes. Your REM stage usually lengthens with each cycle as the night progresses. Sleep disorders can disturb this sleep process.
Polysomnography monitors your sleep stages and cycles to identify if or when your sleep patterns are disrupted.
Doctor may recommend polysomnography if he or she suspects you have:
- Sleep apnea or another sleep-related breathing disorder. In this condition, your breathing repeatedly stops and starts during sleep.
- Periodic limb movement disorder.In this sleep disorder, you involuntarily flex and extend your legs while sleeping. This condition is sometimes associated with restless legs syndrome.
- You experience overwhelming daytime drowsiness and sudden attacks of sleep in this condition.
- REM sleep behavior disorder.This sleep disorder involves acting out dreams as you sleep.
- Unusual behaviors during sleep.Your doctor may perform this test if you do unusual activities during sleep, such as walking, moving around a lot or rhythmic movements.
- Unexplained chronic insomnia.If you consistently have trouble falling asleep or staying asleep, your doctor may recommend polysomnography.
How you prepare
Your doctor may ask you not to drink alcohol or eat or drink anything with caffeine during the afternoon and evening before polysomnography. Alcohol and caffeine can change your sleep patterns, and they may make symptoms of some sleep disorders worse.